Antisweep device for submarine mines



Feb. 15,1955 E. A. JOHNSON 2,702,003

ANTISWEEP DEVICE FOR SUBMARINE MINES Filed Aug. 51, 1942 2 She'ets-Sheet1 gwue/wbo'b LLIS A. JOHNSON Feb. 15, 1955 E. A. JOHNSON 2,702,003

ANTISWEEP DEVICE FOR SUBMARINE MINES Filed Aug. 31, 1942 2 Sheets-Sheet2 United States Patent Oflice Patented Feb. 15, 1955 ANT ISWEEP DEVICEFOR SUBMARINE MINES Ellis A. Johnson, Chevy Chase, Md.

Application August 31, 1942, Serial No. 456,754

21 Claims. (Cl. 102-18) (Granted under Title 35, U. S. Code (1952), sec.266) This invention relates to an anti-sweep device for a submarine'minein which the mine is prevented from being fired by impulses receivedfrom a sweep cable or sweep tail towed by a vessel. More specifically,the invention relates to means operatively connected to a marine mine incommunication with the water within which the mine is planted havingelectro-responsive means operatively connected thereto and controlled bythe gradient of the voltage and current of an electric field set upwithin the water by a sweep cable employing a sea water return as animpulse of electric current is caused to flow through the sweep cablewhereby the mine is prevented from being fired or swept by signalsreceived from the sweep cable.

It is the general practice to employ a sweep cable or tail adapted to betowed by a vessel, hereinafter referred to as a mine sweeper, throughthe water and insulated therefrom throughout the length of the cable, anelectrode being usually provided at the trailing end of the cablethereby to establish an electrical connection between the sweep cableand the water. An electric current is caused to pass through the sweepcable and the aforesaid electrode periodically at predeterminedintervals of time, the current returning by way of the sea water to thehull of the vessel or to an electrode arranged on the trailing end of asecond cable secured to the sweep cable such that the second electrodeis disposed within the water at arelatively short distance from the minesweeper. The passage of the electric current through the sweep cablecauses a strong electromagnetic field to be set up within the water ofsufiicient strength to explode a submarine mine planted within thevicinity of the cable of the type adapted to be fired by changes in theterrestrial magnetic field adjacent thereto. A relatively large electriccurrent is usually passed through the sweep cable thereby to set up anelectromagnetic field thereabout of considerable proportions and thusincrease the effectiveness of the sweep cable, this current, asheretofore stated, being applied at predetermined intervals of time tothe sweep cable. An electromagnetic field is thus set up about the sweepcable periodically at intervals, this electromagnetic field being ofconsiderably greater strength than the magnetic field of a steel vesselwhereby a considerable portion of a mine field is adapted to be swept bya single passage of the towed sweep cable thereacross.

The present invention employs the gradient of the voltage and currentset up within the sea water by the sweep cable to control the operationof a sensitive relay having the winding thereof connected to a pair ofelectrodes secured to the mine casing in insulated relation thereto andin communication with the sea water. The relay is not sufficientlysensitive to be operated by voltage and current gradients set up withinthe water by a passing vessel but of sufficient sensitivity to respondto the relatively larger gradients of voltage and current set up by asweep cable. The relay is employed to disarm the mine for a period oftime suflicient to prevent the firing of the mine by electromagneticsignals received from the sweep cable.

One of the objects of the present invention is the provision of new andimproved means for preventing the firing of a marine mine by signalsreceived from a sweep cable.

Another of the objects is to provide an anti-sweep device for asubmarine mine controlled by the gradient. of the voltage and currentreceived through the water from asweep cable.

Another of the objects is the provision of new and improved meansresponsive to the gradient of the voltage and current of the wateradjacent the mine for disarming the mine until a predetermined periodhas elapsed after the gradient signal has abated.

Still another object is the provision of a new and improved anti-sweepdevice for a submarine mine which will be economical to manufacture,reliable in operation and which possesses all of the qualities ofruggedness and durability.

Still other objects, advantages and improvements will be apparent fromthe following description taken in connection with the accompanyingdrawings wherein like numerals of reference are employed to designatelike parts throughout the several views and in which:

Fig. 1 is a view of a marine mine employing an antisweep deviceaccording to one embodiment of the invention:

Fig. 2 shows in diagrammatic form an arrangement of circuits and partstherefor suitable for use with the mine of Fig. l;

Fig. 3 is a view of a mine employing an'anti-sweep device according toanother form of the invention;

Fig. 4 is a plan view of the mine of Fig. 3; and,

Fig. 5 shows in diagrammatic form an arrangement of circulit s1 andparts suitable for use with the mine of Figs. 3 an Referring now to thedrawings and more particularly to Fig. 1 thereof there is shown thereona submarine mine indicated generally by the numeral 10 arranged on thebed of a body of water within the path of travel of a vessel or sweepcable, as the case may be. The casing 11 of the mine is composed of anynon-magnetic material suitable for the purpose preferably cylindrical inshape and provided with a pair of electrodes 12 and 13 arranged near theopposite ends thereof and insulated from the casing in any suitablemanner as by the insulating members 14 and 15 by means of which theelectrodes are supported by the mine casing. The explosive charge andfiring control mechanism-are arranged within the mine casing in such amanner as to insure that the mine will come to rest in substantially theposition shown on the drawing after being launched within a body ofwater with the electrodes 12 and 13 thereof in contact with the water.The electrodes may be composed of any conductive material suitable forthe purpose but I prefer to use electrodes composed of silver chloridefor this purpose for the reason that this material is adapted tomaintain at all times the electrical potential of the electrodes atsubstantially the potential of the sea water with which they are incontact. The electrodes 12 and 13 are connected to the winding of asensitive relay R as by the conductors 16 and 17 respectively connectedthereto. The relay R is adapted to be operated by a predeterminedgradient of the voltage and current of the sea water with which theelectrodes are in contact such, for example, as may be caused by themagnetic sweep cable 18 within the vicinity of the mine in which the seawater is employed for the return path of the electrical current flowingthrough the cable. The sweep cable 18 is towed through the water by amine sweeper 19 to which the sweep cable is connected and provided witha strong electric current at regular intervals which may be obtainedfrom any suitable source of electrical power 21 such, for example, as astorage battery, the battery being electrically connected to a generatorin such a manner as to maintain the battery in a predetermined chargedcondition, the arrangement also including a circuit closing deviceadapted to connect the sweep cable to the source of electrical power atregular predetermined intervals of time as is well known in the art towhich the present invention pertains.

The mine is provided with a firing control mechanism 22 of the typeadapted to close a firing circuit from a source of potential in responseto a change in the terrestrial magnetic field caused by a vessel withinthe vicinity of the mine, a suitable arming device such, for example, asthe hydrostat 23 being provided to connect the firing mechanism to abattery 24 after a soluble washer S has dissolved or been softenedsufiiciently by the water vto permit the hydrostat to operate. Asensitive relay R is.adapted to apply battery potential to a'tiine'delaydevice TD having a pair of normally closed contacts included within thefiring circuit'ofthe mine therebyto cause the timing device to operateand prevent the detonator 25 from being operated by the firing mechanism22 until sufiicient time has elapsed for the time 'delay'device torelease. -The time'delay device TD isof the slow-torelease type byreason of-the provision of a' dash pot or similar time-delay mechanismwhereby the firingcircuit is adapted to be held open for apredeterminedperiod of time after relay R releases. An arrangement isthus provided in which the closure of the firing circuit at thecontacts'of the time delay deviceis prevented until sufiicient time haselapsed to allow the mine firing mechanism 22 to be restored .to thearmed condition after performing a cycle of firing operations inresponse to the electromagnetic'signal received from the sweep cable Thedetonaton25, it will be understood, is adapted to fire an explosivecharge '26 such, for example, as TNT arranged within the mine casing. 1-Whereason-Figs; l and 2'of the drawings there is shown a marine-mine'ernploying two electrodes. arranged in space relationship atopposite ends of the mine, it will be understood that various otherarrangements of electrons may be employed and the number 'of' theelectrodes may be increased without departing from the presentinvention, Furthermorethe electrodes may be arranged inany suitablemanner such, for example, as circumferentially about the casing of themine in two groups, itbeing merely necessary to connect the electrodesof one group together and to the conductor 16 and the electrodes of theother group to the conductor 17, whereby the gradient of the voltage andcurrent setup within the water by a sweep cable causes the sensitiverelay R to operate and thereby disarm the mine. It willbealsound'erstood that Whereas'in Fig. 2 of the drawings the' armingdevice for the mine firing mechanism 'is'shown as a hydrostat switch. itwill be understood that this is by way of illustration only as variousother arming devices such, for example, as clock'rnechanisms adapted tobe controlled bya hydrostat. arming wire or the like may be employed forarming the mine. On Figs. 3 and 4 is shown a submarine mine'accordingtov another embodiment of the invention, the mine. comprising a casing27 provided with electrodes 28, 29, 31 and 32 arranged in predeterminedspace relation with with respect to one another on thejupper andouterportionof the mine casing 27. The electrodes are composedpreferably' of silver chloride and 'insulated'from'the casing 27 'by theinsulators 33" generally similar to the insulating r'nembers Handof-Fig. 2. The pair of electrodes 28"and 29 are connected to the windingof a sensitive relay-R1, Fig. 5. In a'similar manner the electrodes 31anrl 32 are connected to'the winding of a sensitive relay R2; 'Each ofthe relays R1 and R2 is providedwith apair of normallyopencon'tactsadap'ted to'befclosedas the relay operates. .The contactsare-connected together in parallel-and adapted to closea' circuit frombatteryB to the winding of a time delay mechanism-.TDl wheneverrelaysRlfor R2 operate. When this occurs, 'the armature 34 of the timedelay relay TDI is "operated about thepivotsupportGS thereby quicklyopeningtheipair of contacts 36. :These contacts remain open until apredetermined period of time has elapsed after the operate circuit .tothe time delay mechanism TDl has been interrupted by reason of theprovision of an escapement mechanismadapted to be actuated bya.retractile spring 37 secured to the armature .34 and thereby delay thereturnof the armature. to the unoperated position thereof in;engagementwith the back stop 38 until theaforesaid predetermined period of timehas elapsed. The contacts 36, .it will be understood, are maintaineddisengaged until armature 34 has again movedv into engagement'with theback stop'38fat the completion of the release movement of the armature.

Each of the relays'Rl and "R2 is also provided with a pair of normallyclosed contactsconnected-in' series with the contacts 360ith'e'timefdelay mechanism TD1 andjwithseach other wherebythejfiringfcircuitis opened immediately as relay R1 or R2 operatesandisinaintained opened by thecontacts. 36 until apr'e'det'erminedperiod of time has elapsed afterrelays'RI and R21are'Ire leased.Suitable means are employed: for armingthe mineof Fig' 3 after the-minehas. been launchediandsfor firingthe mine in response to changes inthe-"magnetic new adjaaefit matte, causes by a vessel Within thevicinity of the mine, the hydrostatically controlledarm ing device 39and mine firing mechanism 40, illustrated diagrammatically on Fig. ,5being generally similar to the arming device and mine firing mechanismof Fig. 2.

The operation of the system of Fig. 1 will now be described. Let it beassumed, by way of example, that the mine 10 has been launched within abody of water and thatthe hydrostat-23 thereoj-isoperated therebyoperatively connecting'the battery 24 to the mine firing mechanism 22andv arming the mine. Let it also be assumed that the sweep cable 18 istowed by the mine sweeper 19 within the vicinity of the'mine and thatthe sweep cable has applied thereto atintervals an electric current fromthe source of electrical power 21 of sufficient strength to cause .relayR; to be operated by the current returning'through the's'ea 'waterbetween the electrodes 41 and 42. Th gradient of the voltage and currentbetween the electrodes 12 and 13 of the mine is of sufiicient order ofmagnitude'to'causethe sensitive relay R, Fig. 2, to operate. "When thisoccurs, the firing. circuit is interrupted at armature 30 andbreakcontact of relay R. A c'ircuitis also closed from'the battery 24 bywayof conductor 43, contacts 23'of the arminghydrostat switch, conductor44, make contact and armature 45 ofrelay R, conductor 46, windingoftime'delay relay TD and thence to ground thereby causing relay TD tooperate and at contacts 47 thereof additionally interrupt the firingcireuitforthe detonator 25 The mine firing control mechanism may be ofany type suitable for the purpose such,- for example, as the mine firingmechanism disclosed in Pate'nt 1,446,915 of Ernest F.-Nichols, issuedSeptember 4, 1923 for Submarine Mine in which the firing circuitcontrolled thereby is adapted toxbe closed by .a pair of firing contactsin response to a magnetic signal received by the mine firing mechanism.

By including a break contact of relay R within the firing circuit inseries with'the contacts 47 of relayTD, an arrangement isprovided inwhich the firing circuit is interruptedby' the'operation of thesensitive relay. R before the firing contacts of the mine firingmechanism 22 are closed and the firing'circuit is rendered ineffectiveuntil a predetermined period of time has elapsed after thesensitive'relay R iszreleased, this period of time being controlled-bythe slow releasing relay TD. The time of release of relay TD is longerthanthe time required for the firing mechanism 22 to be restored to thearmed condition in response to the sudden cessation of electromagneticsignals transmitted from a sweep cable. and thusr'the-detonating device25 is prevented from being prematurely'fired'by a protractedinterruption'of the sweep impulses'within theyicinity of the mine asthecontacts: 47 close at the end of the aforesaid predetermined period oftime. r The electric signals received from a sweep cable areoffconsiderably greaterstrength than the signals received from anapproaching'vessel and thus the anti-sweep mechanism comprising theelectrodes. 12 and 13 and the relay Rf'rnay' be madesufiiciently'insensitive for therelay R to' be operated. by the passage.of a vessel. within the vicinitylof the mine. For this reason thecontacts 47 of" the time delay'relayiTD remain closed during .the time avessel is withinjthe vicinity of'the mine .and. at all. othertimes'except when signals. are being received from a sweep'cable' and forapredeterrnined time thereafter. The sensitivity of response of relay Rto the gradient of thevoltage and current of an electric field may beaccomplished in a variety of ways such, for example,'as by including aresistance element in the circuit ,of relay "R in series with thewinding of the relay or in parallelflthereto,'a's'may be desired, but Iprefer. to control-the sensitivity of the relayto current and voltage"gradientreceived by the'electrodes 12 and 13 by the space relationshipor degree .of separation of. the .electrodes 12:and"13 fromeach other.The relay :R'is thus prevented from being operated bybackground currentsproduced from natural causes or by currents received from armovingvessel byreasorr of the'fact that these currentsarewery weak withrespect to the electriccurreritsxproduced,by-..the...sweep cable and,therefore, the anti-sweep arrangement herein'disclosed isrendered'effective to;disarm the'mine whenfthe1relativelyrstrQngcurrents andvvoltage.fgradients.set upfiwithin. the water by;-.a: sweepcable'tare :i'eceivfednbythe'electrodes 12 and 13 and to prevent themine from being disarmed from natural causes or by a vessel disposedwithin the vicinity of the mine.

The operation of the mine of Figs. 3 and 4 in response to electricalimpulses received from a sweep cable will best be understood byconsideration of Fig. 5 on which is shown in diagrammatic form anarrangement of circuits and parts therefor in accordance with analternative form of the invention. Let it be assumed, by way of example,that the mine has been planted within a body of water and that thesoluble washer 50 has dissolved sufiiciently for the hydrostat switch 39to be moved to the closed position thereby closing a circuit frombattery B to the mine firing mechanism and causing the mine to becomearmed. Let it further be assumed that a sweep cable such, for example,as the sweep cable 18 of Fig. l is towed by the mine sweeper 19 withinthe vicinity of the mine and that current impulses are applied theretoby the source of electrical power 21. When this occurs, the gradient ofthe voltage and current picked up by the pair of electrodes 28-29 or3132, as the case may be, is suflicient to operate the sensitive relayR1 or R2 respectively associated therewith. Whether relay R1 or R2 orboth of the relays R1 and R2 are operated, will depend upon the azimuthposition of the mine with respect to the sweep cable. For the purpose ofexplanation it may be assumed that the pair of electrodes 28-29 aregenerally parallel to the sweep cable and'thepair of electrodes 31-32generally perpendicular to the sweep cable. The gradient of the voltageand current picked up by the pair of electrodes 28-29, therefore, willbe considerably greater than the gradient of the voltage and currentpicked up by the pair of electrodes 3132 and thus relay R1 may beassumed to operate as the result of the difference in potential betweenthe electrodes 28 and 29 and relay R2 may be assumed to be unoperated bythe difference in potential between the electrodes 31 and 32.

The operation of relay R1 at armature 49 and make contact thereofapplies ground to conductor 51, winding of the electromagnet of timedelay relay mechanism TD1 from whence the circuit is continued by way ofconductor 52, contacts 39 of the hydrostat switch mechanism and thenceto one terminal of the battery B, the other terminal of battery B beingconnected to ground, thereby-causing the electromagnet of relay TD1 tomove the armature 34 thereof quickly to the operated position. Asarmature 34 of relay TD1 moves away from the back stop 38 the contacts36 of relay TD1 are opened and remain open until armature 34 has againmoved to the released position in engageemnt with the back stop 38, thisreturn movement of the armature being retarded, as heretofore stated, bya suitable escapement mechanism adapted to be actuated by the retractilespring 37 when the operate circuit to relay TD1 is interrupted.

The movement of armature 53 of relay R1 away from its break contact asrelay R1 operates causes the firing circuit for the detonating device 54to be interrupted, the firing circuit including the break contact andarmature 55 of relay R2, contacts 36 of the time delay relay TD1 and asource of electrical power B adapted to-be operatively connected theretoby the firing contacts of the mine firing mechanism 40. An arrangementis thus provided in which the contacts 36 of relay TD1 are opened beforearmature 53 of relay'Rl again moves into engagement with its breakcontact and thus the firing circuit for the detonator 54 is maintainedopen and ineffective until contacts 36 close again at the end of apredetermined period of time after relay R1 releases in response to theabatement or cessation of electric impulses received from the sweepcable. Furthermore, by including the armature 53 and break contact ofrelay R1 within the firing circuit an arrangement is provided in whichthe firing circuit is invariably interrupted by relay R1 beforesufiicient time has elapsed for the firing impulse to be transmittedthereto by the mine firing mechanism in response to the electromagneticsignal received from the sweep cable.

When the flow of current within the sweep cable is discontinued at theexpiration of the first impulse, relay R1 irel'eases and at armature 49thereof interrupts the operate. circuit to the time delay relay TD1. Asthe electromagnet of relay TD1 is deenergized in response to theinterruption of the aforesaid operate circuit the retractile spring 37causes armature 34 to be moved slowly toward the unoperated position,the movement of the armature being retarded by a suitable escapementmechanism. As relay R1 releases, armature 53 moves into engagement withits break contact. The firing circuit, however, is prevented from beingmade effective at this time by contacts 36 of relay TD1 which, it willbe recalled, remain disengaged until a predetermined period of time haselapsed after relay R1 releases. When the second impulse is receivedfrom the sweep cable relay R1 again operates thereby reenergizing theelectromagnet of relay TD1 and causing armature 34 thereof to be movedfrom a partially released position to the fully operated position. Themovement of armature 53 of relay R1 away from its break contactadditionally interrupts the firing circuit. The foregoing cycle ofoperations is continued until the gradient of the voltage and currentbetween the electrodes 28 and 29 has decreased sufficiently to preventthe further operation of relay R1 and relay TD1, therefore, is thuscaused to operate the escapement mechanism thereof for a continuousperiod of time of predetermined length sufiicient to allow the armature34 to be moved by the retractile spring into engagement with the backstop 38 and the contacts 36 thereof to be closed. The firing circuit isnow in readi-- mess to be closed by the mine firing mechanism inresponse to the approach of a vessel within the vicinity of the mine.

In the event that the mine should be disposed on the bed of the body ofwater such that the electrodes 31 and 32 are substantially parallel toor at a small angle with the sweep cable, the gradient of the voltageand current picked up by the electrodes 31 and 32 would be sufiicient tooperate relay R2 and at armature 56 and make contact thereof applyground to one end of the winding of relay TD1 thereby causing relay TD1to operate. As armature 55 of relay R2 moves away from its break contactthe firing circuit to the detonator 54 is interrupted. The successiveoperation of relays R2 and TD1 is repeated as impulses of current andvoltage are received in succession by the electrodes 31 and 32 therebyto maintain the firing circuit continuously interrupted until thecontacts 36 of relay TD1 are closed.

in the event that the mine should be so arranged with respect to thesweep cable that the electrodes 2829 and 31-32 make substantially equalangles with the sweep cable, both the relays R1 and R2 would be operatedconcurrently thereby causing relay TD1 to operate and the contacts 36thereof to be disengaged until the gradient of the voltage and currentreceived by the electrodes was insufficient to operate the relays R1 andR2. The mine is thereby disarmed during this period and for apredetermined period of time thereafter sufiicient to permit thearmature 34 of relay TD1 to be restored to its unoperated position inengagement with the back stop 38. When this occurs, the mine is again inan armed condition.

In each of the foregoing examples it will be understood that the minefiring mechanism 40 is caused to close a pair of firing contacts therebyto apply electrical potential to a portion of the firing circuit whenthe electromagnetic field received by the mine firing mechanism hasundergone a predetermined change and to cause the firing contacts to berestored to an open or disengaged position when the electromagneticsignal received by the mine firing mechanism has ceased or decreased toa predetermined degree of strength.

When an impulse of-electric current flows through the sweep cable theelectric field caused by the flow of this current through the sea wateris relatively large and substantially coincident with theelectromagnetic field set up by the sweep cable. The arrangement of thepairs of electrodes on the mine casing and the sensitive relays R1 andR2 connected thereto is such that the associated sensitive relay iscaused to operate by the electric field of an approaching sweep cablebefore the electromagnetic field set up by the sweep cable has reached adegree of strength necessary to cause the mine firing mechanism to closethe firing contacts thereof and apply electrical energy to the firingcircuit. Furthermore,"when the sweep cable moves away from the mine the;electromagnetic field detected by the mine firing mechanism decreases toa strength insufficient to actuate thefiring con-1 tacts thereof beforethe electric field of the sweep cable. has decreased sufiiciently toprevent the operation ,of the. sensitive relays R1 or R2. The sensitiverelays are therefore invariably operated and the firing circuit renderedinefiective upon-the '5 approach-of a sweep cable within the .vicinityof.'the mine' before *the'mine 'firi n g 'mechanism responds -sufiiciently'to the electromagnetic field of the' sweep cableto'close the firingcontacts thereof and, furthermore, the-firing contacts of the minefiring mechanism are invariably opened whileithesweepcable' is "recedingfrom"the-mine"before the firing circuitis closed bythe release of relay-TD1. in*whi'chthereis no p'ossibility'of firing" the mine as'the result'ofsignals received from a 'sweep'cable;

*Whenever a ponderous mass of magnetic material such, for-example, as a'vessel approaches within the'vicinity of the mine the electromagneticfield adjacent' themine is' altered and when 'the vessel has moved intoa predetermined relative: position with respect to ;the mine thechange-in-the-electromagnetic field' is suflicient'to cause the minefiringimechanism to close the'firin'g contacts thereof and firethe-'detonator '54; RelaysiRl, R2 and TD'l'are unoperated by'themassof-magnetic material for the reason'that the electromagnetic fieldisunaccom= panied by an electricfield ofstrengthsufficient tooperate-thesensitive -relays: t

Brifly statedinsummary, the "present invention pro vide's' an"anti-sweep devicesuitable for usewith asub marine mine orthe'likeadapted to be firedby a change in the magnetic field adjacentthereto'in which the gradient of the voltage and current of anelectric'field is em"- ployed to prevent themine from being fired by asweep cableor sweep tail of 'the type generallyemployed with minesweepers. I

While the invention has been described with*particularity with respecttotwo examples which give satisfactory results it will-'beunderstoodbythose skilled in the art, after understanding the invention, thatvarious changes and'modificat-ions may be'made without departingfrom-the spirit and scone of the invention and it is my intention,therefore,-in the appended claims to cover allsuch changes andmodifications;

The invention herein described and claimed-may be manufactured andused"by or forthe Government of the United States of America forgovernmental purposes without the payment-of any=royaltiesthereon ortherefor.

'What'is claimed 'as new'and desired to be secured by LettersPatent'of-the United States is:

1. 'In a marinemine adapted'to be laid on the bed of a body of wateradjacent the path of travel of a vessel, a casingflfor said mine havingan explosive charge therein, means'responsive to 'a change in themagnetic field adjacent =the mine for-firing saidexplosiv'e charge,means 'included in said lfiring means and adapted when operated torender the'firing means inetie'ctive for a'predetermined interval, andmeans controlled by the gradient of a changing electricfield adjacentthemine for operating'said last namedmeans when said gradient hasreached or exceeded a predetermined value;

2. An anti-sweep device of the character disclosed adapted to control amarine mine,1a'casing for said mine,

firing mechanism within said casing, a firing'circuit' adapted'to'be,closedbysaid firing mechanism in'response to 'a-prede'terminedchange inthe magnetic field adiacent the minefa pair of electrodesin'communication with the water "within which the mine is planted, meansfor supporting said electrodes by said casingin insulated relationtherewith, and electro-responsive means operatively connected to saidelectrodes adapted to interrupt said firing circuit when the gradient ofthe voltage and current within the water between the electrodes reachesa predetermined value.

3. In a submarine mine adapted to be fired by a change inzthe magneticfield adjacent thereto, a firing circuit having 1a detonatingjdevi'c'etherein, a source of electrical energy,'a firing mechanism adapted toclose said firing circuit in response to a predetermined change in saidmagnetic field'thereby to operate said detonating device by said sourceofelectrical energy, a pair of electrodes in contact with the waterwithin which the mine :issubmerged, means :for maintainingisaidelectrodes in predetermined-spaced rrelation with respect to each other,and anz'feleetro-responsive device operatively connected to said pairofelectrodes adapted to vbe operated'when the gradienti ofthevoltage andcurrent within the'wate'r between :the electrodesreaches a predetermined"value,

said electro responsive"device having means for inter-' An'arrangementiis' thus provided 4. In a submarine mine adapted to-befired b yja'ch ange" in the magnetic field adjacent'thereto, a'firingcirfcuit havinga'detonating device-therein, a: sourceofelec'trical energy, a firing mechanis'madaptedto close"-said"firi'ng.circuit in response'to a'predetermined change in'saijdimage' netic fieldthereby' to operate said 'detonatin'g idevice"by7 the source ofelectricalfenergy, apair'of electrodesin' contact with the 'waterwithinwhich the minefis sub merged, means for maintaining said electrodes inprede termined'spaced relation withrespect toeach othely'anelectro-responsive device operatively connected to said. pair ofelectrodes adapted to be operated whenfthej'gradi ent of the voltage andcurrent within the-water between the electrodes reaches a predeterminedvalue, saidelectroresponsive device having means for interrupting said-fir-" ing c'ircuitas the electro-responsive deviceoperates,";and meanscontrolled by said electro re'sponsive"device fol additionallyinterrupting ,said firing pcircuit fora prede terminedperiod of timeaftertheelectro-responsive device has released. p g

5. A mine of the characterfdi'sclosedfladapted tobe laid on the bed of'a' bodyof water withinthe'ipath-ot travel of a vessel, anexplosivecharge -arranged*within said mine, a detonating deviceadaptedto'explo'de s'aid' explosive charge, a normally open firingcircuit--including a source of electrical energy, adapted to firesaidden onating device, -means responsive to themagnetic field' adjacent themine adapted to close said firingcircuit when the magnetic field hasbeen altered by a predeterf mined amount, and means controlled by-' thegradient of an electric field adjacent the mine for preventing' theclosure'of thefiring-circuit by said, circuitclosing means when thegradient has increased to a predetermined value:

6. A .mine 'of the character disclosed adapted to be laid on the bed-ofa body of water withinthe-pathfof travel of a vessel, an. explosivechargearrangedwithin said mine, a detonating device "adaptedtoexplode'naid explosive charge,- anormallyopen firing circuitincluding" a source of electrical energy adapted tofire'said' detonatingdevice, means responsiveto'the magneticfiel'd adja' cent the mineadapted 'to close said firing *circuit when the magnetic'field hasbeenaltered by,a'predetermined" amount, electrore'sp-onsive means controlledbyfl'the gradient of an electric field'adj acentthe minetorpre ventingthe closure of the firings cir'cuitbysaid circuit closing means when thegradient has increased to a" predetermined value, and means controlledby said electr-oresponsive means for additionally preventing theclosure-of the firing circuit by said circuit'closingmeans until apredetermined period of time has'elapsedmfter the gradient has decreasedto' a predetermined value: 7

' 7. A submarine mine having an explosive charge therein,- means forarmingthe mine, meansinclu din'gia' device responsive to ach'ange in themagnetic'field ad jacent the mine for firing said' explosive charge-whenthe mine has been armed by said arming means,':con-' trol means includedwithin said firing means 'anda'dapt ed to render the firing meansineffective when "a prede' termined value of voltage is applied theretoand "means responsive to an electric field adjacent thereto 'forapplyingsaid voltage to said control means when the gradient of theelectric-field reaches a predetermined value;

8. A marine mine of the character disclosed 'havingan explosive chargetherein, means responsive to the'pressure of the water within which themine is planted for arming the mine, a detonatingdevice-adapted to "firesaid explosive charge, a minefiring circuit including said detonatingdevice, means included in said "firing'circuitfor operating thedetonating device in response-'to a'pre determined changein the magneticfield adjacent thereto when themine has been armed by said armingmeans,means included in said firing circuit and'adaptedwhen operated tointerrupt the firing circuit for"a'prede'ter-' mined interval and meanscontrolled .by thefgradientof an electric field adjacent themine .foroperating said interrupting means thereby to disarm .the -mine when thegradient of .the electric field reaches 'orz-exceeds' apredetermined-value. r H

9. In a submarine mineadaptedlto be fired bya change in themagneticfield adjacent thereto, a casingQfon-saidmine, firing mechanism within.said -casing,,,a firing fill}: cuit"adapted tobe c-losedbytsaidSfii'ing,mechanism in response to a predeterminedcha'nge inth'e'magneticfield adjacent the mine, a pair of electrodes in contactwith the water within which the mine is planted, a second pair ofelectrodes in communication with the water, means supported by saidcasing for maintaining each pair of electrodes in predetermined spacedrelation with respect to the other pair of electrodes, a pair ofelectroresponsive devices respectively connected to each of said pairsof electrodes and adapted to be operated by the gradient of the voltageand current in the water there- 'between, each of saidelectro-responsive devices having means adapted to interrupt said firingcircuit as the electro-responsive device operates, and means adapted tobe controlled by either of said electro-responsive devices foradditionally interrupting said firing circuit for a predetermined periodof time after the electro-responsive device has released.

10. A marine mine of the character disclosed having an explosive chargetherein, means for arming the mine, a firing circuit having a detonatingdevice therein adapted to explode said explosive charge as the firingcircuit is closed, firing mechanism adapted to close said firing circuitin response to a predetermined change in the magnetic field adjacent themine, a pair of electro-responsive devices adapted to interrupt saidfiring circuit as either of the devices operates, a plurality ofelectrodes in contact with the water within which the mine is plantedoperatively connected to said electro-responsive devices and adapted tooperate the electro-responsive devices when the gradient of an electricfield within the water adjacent the mine reaches or exceeds apredetermined value, and means controlled by said electro-responsivedevices for preventing the closure of the firing circuit by said firingmechanism until a predetermined period of of time has elapsed after theelectro-responsive devices have released.

11. An anti-sweep device of the character disclosed adapted to prevent amarine mine from being fired by signals received from a sweep cable, acasing for said mine having an explosive charge therein, means fordetonating the explosive charge, a firing circuit, firing mechanismresponsive to a change in the magnetic field adjacent the mine adaptedto close said firing circuit and thereby operate said detonating means,a sensitive relay adapted to interrupt said firing circuit as the relayoperates, and means including a pair of electrodes in contact with thewater for causing said sensitive relay to interrupt said firing circuitin response to a predetermined gradient of the electric field receivedfrom the sweep wire before the firing circuit is closed by said firingmechanism.

12. In a submarine mine arranged within a body of water and adapted tobe fired by a change in the magnetic field adjacent thereto, a casingfor said mine having an explosive charge therein, means responsive to achange in the magnetic field adjacent the mine for firing said explosivecharge, a firing circuit connected to said firing means,electro-responsive means controlled by the gradient of an electric fieldadjacent the mine for interrupting said firing circuit in response to anelectric impulse received through the water from a sweep cable, andmeans controlled by said electro-responsive means for maintaining saidfiring circuit continuously interrupted while a plurality of electricimpulses from said sweep cable are received in succession and for apredetermined period of time after said impulses have ceased.

13. A mine of the character disclosed adapted to be laid on the bed of abody of water within the path of travel of a vessel, an explosive chargearranged within said mine, a detonating device adapted to explode saidexplosive charge, a normally open firing circuit including a source ofelectrical energy adapted to fire said detonating device as the firingcircuit is closed, means responsive to the magnetic field adjacent themine adapted to close said firing circuit when said magnetic field hasbeen altered by a predetermined amount, electro-responsive meanscontrolled by the current and voltage gradient of an electric field setup with-in the water by a sweep cable, said electro-responsive meanshaving a pair of contacts adapted to interrupt said firing circuit, and:means controlled by said electro-responsive means for maintaining saidfiring circuit continuously interrupted while the electro-responsivemeans operates successively in response to a plurality ofelectromagnetic fields received in succession from the sweep cable.

14. In a submarine mine adapted to be fired by a 10 i p change in themagnetic field adjacentthereto, a casing for said mine, firing mechanismdisposed within said casing adapted to be operated by a predeterminedchange in said magnetic field, a firing circuit adapted to be closed bysaid firing mechanism, a sensitive relay having means for interruptingsaid firing circuit as the relay operates, means including a pair ofelectrodes in contact-with the water adapted to operate said sensitiverelay in response to a predetermined current and gradient of the voltageof the electric field received from a sweep cable as the sweep cableapproaches the mine thereby to interrupt said firing circuit before thefiring mechanism operates in response to a change in said magnetic fieldcaused by the electromagnet field set up by the sweep cable, and meanscontrolled by said sensitive relay for maintaining the firing circuitcontinuously interrupted until the sweep cable has passed beyond themine to a safe distance therefrom such that the electromagnetic fieldreceived from the sweep cable is of insuflicient strength to operatesaid firing mechanism.

15. In a marine mine in combination, a firing circuit, a pair ofelectrodes in communication with the surrounding water carried by saidmine, and a relay having the winding thereof connected to saidelectrodes and a pair of contacts included in said firing circuit forinterrupting said circuit as the relay operates in response to apredetermined value of voltage and current gradient sensed by saidelectrodes.

16. In a mine of the character disclosed, a firing circuit, magneticallycontrolled means for closing said circu-it, a pair of electrodes incommunication with the surrounding water, and means controlled by saidelectrodes as an electric field adjacent the mine is sensed thereby forinterrupting said circuit in response to a magnetic sweep operationbefore the circuit is closed by said magnetically controlled circuitclosing means.

17. In a marine mine, a pair of electrodes disposed in mutually spacedrelation in communication with the surrounding water for sensing agradient of an electric field, an electroresponsive device operativelyconnected to said electrodes and adapted to be operated by a currentreceived therefrom as the gradient is sensed by the electrodes, saiddevice having a pair of normally closed contacts adapted to bedisengaged as the device operates, and a mine firing circuit connectedin series with said pair of contacts whereby the firing circuit isinterrupted as the gradient of an electric field is sensed by saidelectrodes.

18. In a submarine mine adapted to be fired by a change in the magneticfield adjacent thereto, means including a normally open circuit forfiring the mine when the circuit is closed, means for closing saidcircuit in response to a predetermined change in the magnetic fieldadjacent thereto as a vessel moves within the vicinity thereof,electroresponsive means for preventing the closure of said circuit whenthe gradient of the voltage and current of an electric field caused by amine sweeping operation has increased to a predetermined value, and apair of sensing electrodes in communication with the surrounding waterfor actuating said electroresponsive means as said gradient is sensedthereby.

19. In a marine mine, the combination of an initially unarmed firingcircuit including an electroresponsive detonator, means responsive to achange in the magnetic field adjacent the mine for closing said firingcircuit when said magnetic field has been altered by a predeterminedamount, and means responsive to the gradient of an electric fieldadjacent the mine for preventing closure of the firing circuit by saidmagnetic field responsive means when said gradient has increased to apredetermined value, said gradient responsive means including at leasttwo electrodes carried by the mine in mutually spaced relation and incommunication with the surrounding water.

20. In a marine mine, an electroresponsive detonator, a firing circuitfor the detonator including a normally open switch and a normally closedswitch, means responsive to a change in the magnetic field adjacent themine for closing the normally open switch, and means controlled by anelectric field adjacent the mine for opening said normally closed switchin response to an electric impulse received through the water from amagnetic sweep cable, said last named means including a pair ofelectrodes in communication with the surrounding water for sensing saidfield.

21. In a firing mechanism for a marine mine, in comginatipn means includingemegneie respqnsivfielemen, 7 References Cited in the file of thispatent Qr'fii'ifigthe'mine; a'pfiir'ofdectw ve's'irll'mutua y space Trelatiin commfini'ca'tibn wi h the'sui'l ounding water, UNITED TPATENTS. az'i'd an el 'e ctrbrd 'jjdflsivjdevice operatively connectedto 310,568 7 Healpeff'alp I1 1ly'22', 191 9. sai d"e1ect r0des;andhaving means forrendering the"n1ag- 5 1,382,374 Maxim Jnne. '21,-1921netiefiiingelement' ineffective tofir'e the mine when the 1,466,915Nichols Sep'tf4, 1923 gr'a dient'of an electric. field between saidelectrodes is sliflici'en't' to operate said electroresponsi've' means.

